Nitzsche and Wick, U.S. Pat. No. 3,065,194 disclose a family of silicone rubber compositions comprising an essentially anhydrous mixture of (1) a linear organosiloxane polymer having hydroxyl terminal groups, (2) a polyfunctional organosilicone cross-linking agent, and (3) a metal salt, chelate, organometallic compound, acid or base, which serves as a cross-linking catalyst. Such compositions vulcanize or cure to rubbery solids when exposed to moisture and this makes them uniquely useful, in that they can be maintained over a long period of time in a single container, e.g., sealed in caulking tubes, ready for use, but then the user can apply the material and bring it into contact with water or water vapor to cure it. Such compositions are useful in sealants, electrical insulation, coatings, dental cement, caulking compounds, expansion joints, gaskets, shock absorbers, adhesives, and in many other forms.
Additional background teachings relating to one-package room temperature vulcanizing silicone compositions are to be found in Bruner, U.S. Pat. No. 3,035,016 and in Ceyzeriat, U.S. Pat. No. 3,133,891, who deal with one-package, moisture curable compositions comprising the reaction products of acyloxy-substituted silanes and hydroxylated siloxanes, the compositions curing with the liberation of acid fragments and the curing being promoted with various agents, such as organic derivatives of tin. Also of interest is Brown et al, U.S. Pat. No. 3,161,614, who show a pre-reacted silanol end-stopped diorganopolysiloxane and cross-linker, in combination with a cross-linking catalyst; Cooper; U.S. Pat. No. 3,383,355, who deals with the preparation of an alkoxy-terminated linear siloxane polymer using a neutral, finely divided solid catalyst, e.g., fuller's earth; Matherly, U.S. Pat. No. 3,499,859, who uses a hydrocarbonoxy end-blocked dioorganopolysiloxane and a metal-containing curing catalyst along with boron nitride; and Cooper et al, U.S. Pat. No. 3,542,901, who use a mixture of a linear siloxane having di- or tri-functional end-blocking units with a linear siloxane having chemically nonfunctional inert and end-blocking units on one end and di- or tri-functional end-blocking units on the other, and include a catalyst and a cross-linker. Additionally, of interest are Brown et al, U.S. Pat. No. 3,122,522, who combine organopolysiloxane intermediates containing condensable "cellosolvoxyl" groups with a catalyst; Brown et al, U.S. Pat. No. 3,170,894, who combine organopolysiloxane intermediates containing condensable polyhydrocarbonoxy type radicals with a catalyst; and Weyenberg, U.S. Pat. No. 3,175,993, who combines organopolysiloxane intermediates end-blocked with alkoxylated silcarbane groups with a catalyst. Smith and Hamilton, U.S. Pat. Nos. 3,689,454 and 3,779,986, Weyenberg, U.S. Pat. Nos. 3,294,739 and 3,334,067, and Clark et al, U.S. Pat. No. 3,719,635 also disclose one-package compositions.
Applicant's U.S. Pat. No. 3,382,205 is also of interest because it discloses one package systems, which are moisture curable and which further contain mono-, di- and trialkylpolysiloxanes, the latter fluids functioning as adhesion promoters and processing aids.
All of the foregoing patents are fully incorporated herein by reference.
A special family of compositions is known to provide sealants with fairly high temperature resistance, but these are of limited utility as gasketing materials in the automotive industry in those instances where odor and corrosion can cause problems. By way of illustration, a composition comprising a silanol-terminated polydimethylsiloxane, methyltriacetoxysilane fumed silica filler and dibutyltindilaurate, is presently used in most applications but is not entirely satisfactory in some areas because it eliminates acetic acid upon curing. This cure by-product is responsible for the objectionable odor and corrosion referred to above. The presently used compositions also tend to have a relatively high degree of adhesion at low temperatures so that, for example, if a new automobile engine has to be disassembled before being put in place and operated, it is difficult to repair without damaging such things as oil pans and valve covers.
It has now been found possible to provide a low-odor, non-corrosive fast curing one-component RTV composition which exhibits, after curing by moisture, excellent oil resistance and, especially with a thermal stabilizer, high temperature resistance properties. The composition also has a low degree of adhesion at room temperature, but this improves at high temperature, thereby accomplishing a good seal, e.g., when an automobile engine is started with gasketing producing from the instant composition. They are useful in a variety of conventional applications, and particularly as gasket layers between metal surfaced parts.